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1/*
2 * at24.c - handle most I2C EEPROMs
3 *
4 * Copyright (C) 2005-2007 David Brownell
5 * Copyright (C) 2008 Wolfram Sang, Pengutronix
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License as published by
9 * the Free Software Foundation; either version 2 of the License, or
10 * (at your option) any later version.
11 */
12#include <linux/kernel.h>
13#include <linux/init.h>
14#include <linux/module.h>
15#include <linux/slab.h>
16#include <linux/delay.h>
17#include <linux/mutex.h>
18#include <linux/mod_devicetable.h>
19#include <linux/log2.h>
20#include <linux/bitops.h>
21#include <linux/jiffies.h>
22#include <linux/of.h>
23#include <linux/acpi.h>
24#include <linux/i2c.h>
25#include <linux/nvmem-provider.h>
26#include <linux/regmap.h>
27#include <linux/platform_data/at24.h>
28
29/*
30 * I2C EEPROMs from most vendors are inexpensive and mostly interchangeable.
31 * Differences between different vendor product lines (like Atmel AT24C or
32 * MicroChip 24LC, etc) won't much matter for typical read/write access.
33 * There are also I2C RAM chips, likewise interchangeable. One example
34 * would be the PCF8570, which acts like a 24c02 EEPROM (256 bytes).
35 *
36 * However, misconfiguration can lose data. "Set 16-bit memory address"
37 * to a part with 8-bit addressing will overwrite data. Writing with too
38 * big a page size also loses data. And it's not safe to assume that the
39 * conventional addresses 0x50..0x57 only hold eeproms; a PCF8563 RTC
40 * uses 0x51, for just one example.
41 *
42 * Accordingly, explicit board-specific configuration data should be used
43 * in almost all cases. (One partial exception is an SMBus used to access
44 * "SPD" data for DRAM sticks. Those only use 24c02 EEPROMs.)
45 *
46 * So this driver uses "new style" I2C driver binding, expecting to be
47 * told what devices exist. That may be in arch/X/mach-Y/board-Z.c or
48 * similar kernel-resident tables; or, configuration data coming from
49 * a bootloader.
50 *
51 * Other than binding model, current differences from "eeprom" driver are
52 * that this one handles write access and isn't restricted to 24c02 devices.
53 * It also handles larger devices (32 kbit and up) with two-byte addresses,
54 * which won't work on pure SMBus systems.
55 */
56
57struct at24_data {
58 struct at24_platform_data chip;
59 int use_smbus;
60 int use_smbus_write;
61
62 /*
63 * Lock protects against activities from other Linux tasks,
64 * but not from changes by other I2C masters.
65 */
66 struct mutex lock;
67
68 u8 *writebuf;
69 unsigned write_max;
70 unsigned num_addresses;
71
72 struct regmap_config regmap_config;
73 struct nvmem_config nvmem_config;
74 struct nvmem_device *nvmem;
75
76 /*
77 * Some chips tie up multiple I2C addresses; dummy devices reserve
78 * them for us, and we'll use them with SMBus calls.
79 */
80 struct i2c_client *client[];
81};
82
83/*
84 * This parameter is to help this driver avoid blocking other drivers out
85 * of I2C for potentially troublesome amounts of time. With a 100 kHz I2C
86 * clock, one 256 byte read takes about 1/43 second which is excessive;
87 * but the 1/170 second it takes at 400 kHz may be quite reasonable; and
88 * at 1 MHz (Fm+) a 1/430 second delay could easily be invisible.
89 *
90 * This value is forced to be a power of two so that writes align on pages.
91 */
92static unsigned io_limit = 128;
93module_param(io_limit, uint, 0);
94MODULE_PARM_DESC(io_limit, "Maximum bytes per I/O (default 128)");
95
96/*
97 * Specs often allow 5 msec for a page write, sometimes 20 msec;
98 * it's important to recover from write timeouts.
99 */
100static unsigned write_timeout = 25;
101module_param(write_timeout, uint, 0);
102MODULE_PARM_DESC(write_timeout, "Time (in ms) to try writes (default 25)");
103
104#define AT24_SIZE_BYTELEN 5
105#define AT24_SIZE_FLAGS 8
106
107#define AT24_BITMASK(x) (BIT(x) - 1)
108
109/* create non-zero magic value for given eeprom parameters */
110#define AT24_DEVICE_MAGIC(_len, _flags) \
111 ((1 << AT24_SIZE_FLAGS | (_flags)) \
112 << AT24_SIZE_BYTELEN | ilog2(_len))
113
114static const struct i2c_device_id at24_ids[] = {
115 /* needs 8 addresses as A0-A2 are ignored */
116 { "24c00", AT24_DEVICE_MAGIC(128 / 8, AT24_FLAG_TAKE8ADDR) },
117 /* old variants can't be handled with this generic entry! */
118 { "24c01", AT24_DEVICE_MAGIC(1024 / 8, 0) },
119 { "24c02", AT24_DEVICE_MAGIC(2048 / 8, 0) },
120 /* spd is a 24c02 in memory DIMMs */
121 { "spd", AT24_DEVICE_MAGIC(2048 / 8,
122 AT24_FLAG_READONLY | AT24_FLAG_IRUGO) },
123 { "24c04", AT24_DEVICE_MAGIC(4096 / 8, 0) },
124 /* 24rf08 quirk is handled at i2c-core */
125 { "24c08", AT24_DEVICE_MAGIC(8192 / 8, 0) },
126 { "24c16", AT24_DEVICE_MAGIC(16384 / 8, 0) },
127 { "24c32", AT24_DEVICE_MAGIC(32768 / 8, AT24_FLAG_ADDR16) },
128 { "24c64", AT24_DEVICE_MAGIC(65536 / 8, AT24_FLAG_ADDR16) },
129 { "24c128", AT24_DEVICE_MAGIC(131072 / 8, AT24_FLAG_ADDR16) },
130 { "24c256", AT24_DEVICE_MAGIC(262144 / 8, AT24_FLAG_ADDR16) },
131 { "24c512", AT24_DEVICE_MAGIC(524288 / 8, AT24_FLAG_ADDR16) },
132 { "24c1024", AT24_DEVICE_MAGIC(1048576 / 8, AT24_FLAG_ADDR16) },
133 { "at24", 0 },
134 { /* END OF LIST */ }
135};
136MODULE_DEVICE_TABLE(i2c, at24_ids);
137
138static const struct acpi_device_id at24_acpi_ids[] = {
139 { "INT3499", AT24_DEVICE_MAGIC(8192 / 8, 0) },
140 { }
141};
142MODULE_DEVICE_TABLE(acpi, at24_acpi_ids);
143
144/*-------------------------------------------------------------------------*/
145
146/*
147 * This routine supports chips which consume multiple I2C addresses. It
148 * computes the addressing information to be used for a given r/w request.
149 * Assumes that sanity checks for offset happened at sysfs-layer.
150 */
151static struct i2c_client *at24_translate_offset(struct at24_data *at24,
152 unsigned *offset)
153{
154 unsigned i;
155
156 if (at24->chip.flags & AT24_FLAG_ADDR16) {
157 i = *offset >> 16;
158 *offset &= 0xffff;
159 } else {
160 i = *offset >> 8;
161 *offset &= 0xff;
162 }
163
164 return at24->client[i];
165}
166
167static ssize_t at24_eeprom_read(struct at24_data *at24, char *buf,
168 unsigned offset, size_t count)
169{
170 struct i2c_msg msg[2];
171 u8 msgbuf[2];
172 struct i2c_client *client;
173 unsigned long timeout, read_time;
174 int status, i;
175
176 memset(msg, 0, sizeof(msg));
177
178 /*
179 * REVISIT some multi-address chips don't rollover page reads to
180 * the next slave address, so we may need to truncate the count.
181 * Those chips might need another quirk flag.
182 *
183 * If the real hardware used four adjacent 24c02 chips and that
184 * were misconfigured as one 24c08, that would be a similar effect:
185 * one "eeprom" file not four, but larger reads would fail when
186 * they crossed certain pages.
187 */
188
189 /*
190 * Slave address and byte offset derive from the offset. Always
191 * set the byte address; on a multi-master board, another master
192 * may have changed the chip's "current" address pointer.
193 */
194 client = at24_translate_offset(at24, &offset);
195
196 if (count > io_limit)
197 count = io_limit;
198
199 if (at24->use_smbus) {
200 /* Smaller eeproms can work given some SMBus extension calls */
201 if (count > I2C_SMBUS_BLOCK_MAX)
202 count = I2C_SMBUS_BLOCK_MAX;
203 } else {
204 /*
205 * When we have a better choice than SMBus calls, use a
206 * combined I2C message. Write address; then read up to
207 * io_limit data bytes. Note that read page rollover helps us
208 * here (unlike writes). msgbuf is u8 and will cast to our
209 * needs.
210 */
211 i = 0;
212 if (at24->chip.flags & AT24_FLAG_ADDR16)
213 msgbuf[i++] = offset >> 8;
214 msgbuf[i++] = offset;
215
216 msg[0].addr = client->addr;
217 msg[0].buf = msgbuf;
218 msg[0].len = i;
219
220 msg[1].addr = client->addr;
221 msg[1].flags = I2C_M_RD;
222 msg[1].buf = buf;
223 msg[1].len = count;
224 }
225
226 /*
227 * Reads fail if the previous write didn't complete yet. We may
228 * loop a few times until this one succeeds, waiting at least
229 * long enough for one entire page write to work.
230 */
231 timeout = jiffies + msecs_to_jiffies(write_timeout);
232 do {
233 read_time = jiffies;
234 if (at24->use_smbus) {
235 status = i2c_smbus_read_i2c_block_data_or_emulated(client, offset,
236 count, buf);
237 } else {
238 status = i2c_transfer(client->adapter, msg, 2);
239 if (status == 2)
240 status = count;
241 }
242 dev_dbg(&client->dev, "read %zu@%d --> %d (%ld)\n",
243 count, offset, status, jiffies);
244
245 if (status == count)
246 return count;
247
248 /* REVISIT: at HZ=100, this is sloooow */
249 msleep(1);
250 } while (time_before(read_time, timeout));
251
252 return -ETIMEDOUT;
253}
254
255static ssize_t at24_read(struct at24_data *at24,
256 char *buf, loff_t off, size_t count)
257{
258 ssize_t retval = 0;
259
260 if (unlikely(!count))
261 return count;
262
263 /*
264 * Read data from chip, protecting against concurrent updates
265 * from this host, but not from other I2C masters.
266 */
267 mutex_lock(&at24->lock);
268
269 while (count) {
270 ssize_t status;
271
272 status = at24_eeprom_read(at24, buf, off, count);
273 if (status <= 0) {
274 if (retval == 0)
275 retval = status;
276 break;
277 }
278 buf += status;
279 off += status;
280 count -= status;
281 retval += status;
282 }
283
284 mutex_unlock(&at24->lock);
285
286 return retval;
287}
288
289/*
290 * Note that if the hardware write-protect pin is pulled high, the whole
291 * chip is normally write protected. But there are plenty of product
292 * variants here, including OTP fuses and partial chip protect.
293 *
294 * We only use page mode writes; the alternative is sloooow. This routine
295 * writes at most one page.
296 */
297static ssize_t at24_eeprom_write(struct at24_data *at24, const char *buf,
298 unsigned offset, size_t count)
299{
300 struct i2c_client *client;
301 struct i2c_msg msg;
302 ssize_t status = 0;
303 unsigned long timeout, write_time;
304 unsigned next_page;
305
306 /* Get corresponding I2C address and adjust offset */
307 client = at24_translate_offset(at24, &offset);
308
309 /* write_max is at most a page */
310 if (count > at24->write_max)
311 count = at24->write_max;
312
313 /* Never roll over backwards, to the start of this page */
314 next_page = roundup(offset + 1, at24->chip.page_size);
315 if (offset + count > next_page)
316 count = next_page - offset;
317
318 /* If we'll use I2C calls for I/O, set up the message */
319 if (!at24->use_smbus) {
320 int i = 0;
321
322 msg.addr = client->addr;
323 msg.flags = 0;
324
325 /* msg.buf is u8 and casts will mask the values */
326 msg.buf = at24->writebuf;
327 if (at24->chip.flags & AT24_FLAG_ADDR16)
328 msg.buf[i++] = offset >> 8;
329
330 msg.buf[i++] = offset;
331 memcpy(&msg.buf[i], buf, count);
332 msg.len = i + count;
333 }
334
335 /*
336 * Writes fail if the previous one didn't complete yet. We may
337 * loop a few times until this one succeeds, waiting at least
338 * long enough for one entire page write to work.
339 */
340 timeout = jiffies + msecs_to_jiffies(write_timeout);
341 do {
342 write_time = jiffies;
343 if (at24->use_smbus_write) {
344 switch (at24->use_smbus_write) {
345 case I2C_SMBUS_I2C_BLOCK_DATA:
346 status = i2c_smbus_write_i2c_block_data(client,
347 offset, count, buf);
348 break;
349 case I2C_SMBUS_BYTE_DATA:
350 status = i2c_smbus_write_byte_data(client,
351 offset, buf[0]);
352 break;
353 }
354
355 if (status == 0)
356 status = count;
357 } else {
358 status = i2c_transfer(client->adapter, &msg, 1);
359 if (status == 1)
360 status = count;
361 }
362 dev_dbg(&client->dev, "write %zu@%d --> %zd (%ld)\n",
363 count, offset, status, jiffies);
364
365 if (status == count)
366 return count;
367
368 /* REVISIT: at HZ=100, this is sloooow */
369 msleep(1);
370 } while (time_before(write_time, timeout));
371
372 return -ETIMEDOUT;
373}
374
375static ssize_t at24_write(struct at24_data *at24, const char *buf, loff_t off,
376 size_t count)
377{
378 ssize_t retval = 0;
379
380 if (unlikely(!count))
381 return count;
382
383 /*
384 * Write data to chip, protecting against concurrent updates
385 * from this host, but not from other I2C masters.
386 */
387 mutex_lock(&at24->lock);
388
389 while (count) {
390 ssize_t status;
391
392 status = at24_eeprom_write(at24, buf, off, count);
393 if (status <= 0) {
394 if (retval == 0)
395 retval = status;
396 break;
397 }
398 buf += status;
399 off += status;
400 count -= status;
401 retval += status;
402 }
403
404 mutex_unlock(&at24->lock);
405
406 return retval;
407}
408
409/*-------------------------------------------------------------------------*/
410
411/*
412 * Provide a regmap interface, which is registered with the NVMEM
413 * framework
414*/
415static int at24_regmap_read(void *context, const void *reg, size_t reg_size,
416 void *val, size_t val_size)
417{
418 struct at24_data *at24 = context;
419 off_t offset = *(u32 *)reg;
420 int err;
421
422 err = at24_read(at24, val, offset, val_size);
423 if (err)
424 return err;
425 return 0;
426}
427
428static int at24_regmap_write(void *context, const void *data, size_t count)
429{
430 struct at24_data *at24 = context;
431 const char *buf;
432 u32 offset;
433 size_t len;
434 int err;
435
436 memcpy(&offset, data, sizeof(offset));
437 buf = (const char *)data + sizeof(offset);
438 len = count - sizeof(offset);
439
440 err = at24_write(at24, buf, offset, len);
441 if (err)
442 return err;
443 return 0;
444}
445
446static const struct regmap_bus at24_regmap_bus = {
447 .read = at24_regmap_read,
448 .write = at24_regmap_write,
449 .reg_format_endian_default = REGMAP_ENDIAN_NATIVE,
450};
451
452/*-------------------------------------------------------------------------*/
453
454#ifdef CONFIG_OF
455static void at24_get_ofdata(struct i2c_client *client,
456 struct at24_platform_data *chip)
457{
458 const __be32 *val;
459 struct device_node *node = client->dev.of_node;
460
461 if (node) {
462 if (of_get_property(node, "read-only", NULL))
463 chip->flags |= AT24_FLAG_READONLY;
464 val = of_get_property(node, "pagesize", NULL);
465 if (val)
466 chip->page_size = be32_to_cpup(val);
467 }
468}
469#else
470static void at24_get_ofdata(struct i2c_client *client,
471 struct at24_platform_data *chip)
472{ }
473#endif /* CONFIG_OF */
474
475static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
476{
477 struct at24_platform_data chip;
478 kernel_ulong_t magic = 0;
479 bool writable;
480 int use_smbus = 0;
481 int use_smbus_write = 0;
482 struct at24_data *at24;
483 int err;
484 unsigned i, num_addresses;
485 struct regmap *regmap;
486
487 if (client->dev.platform_data) {
488 chip = *(struct at24_platform_data *)client->dev.platform_data;
489 } else {
490 if (id) {
491 magic = id->driver_data;
492 } else {
493 const struct acpi_device_id *aid;
494
495 aid = acpi_match_device(at24_acpi_ids, &client->dev);
496 if (aid)
497 magic = aid->driver_data;
498 }
499 if (!magic)
500 return -ENODEV;
501
502 chip.byte_len = BIT(magic & AT24_BITMASK(AT24_SIZE_BYTELEN));
503 magic >>= AT24_SIZE_BYTELEN;
504 chip.flags = magic & AT24_BITMASK(AT24_SIZE_FLAGS);
505 /*
506 * This is slow, but we can't know all eeproms, so we better
507 * play safe. Specifying custom eeprom-types via platform_data
508 * is recommended anyhow.
509 */
510 chip.page_size = 1;
511
512 /* update chipdata if OF is present */
513 at24_get_ofdata(client, &chip);
514
515 chip.setup = NULL;
516 chip.context = NULL;
517 }
518
519 if (!is_power_of_2(chip.byte_len))
520 dev_warn(&client->dev,
521 "byte_len looks suspicious (no power of 2)!\n");
522 if (!chip.page_size) {
523 dev_err(&client->dev, "page_size must not be 0!\n");
524 return -EINVAL;
525 }
526 if (!is_power_of_2(chip.page_size))
527 dev_warn(&client->dev,
528 "page_size looks suspicious (no power of 2)!\n");
529
530 /* Use I2C operations unless we're stuck with SMBus extensions. */
531 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
532 if (chip.flags & AT24_FLAG_ADDR16)
533 return -EPFNOSUPPORT;
534
535 if (i2c_check_functionality(client->adapter,
536 I2C_FUNC_SMBUS_READ_I2C_BLOCK)) {
537 use_smbus = I2C_SMBUS_I2C_BLOCK_DATA;
538 } else if (i2c_check_functionality(client->adapter,
539 I2C_FUNC_SMBUS_READ_WORD_DATA)) {
540 use_smbus = I2C_SMBUS_WORD_DATA;
541 } else if (i2c_check_functionality(client->adapter,
542 I2C_FUNC_SMBUS_READ_BYTE_DATA)) {
543 use_smbus = I2C_SMBUS_BYTE_DATA;
544 } else {
545 return -EPFNOSUPPORT;
546 }
547 }
548
549 /* Use I2C operations unless we're stuck with SMBus extensions. */
550 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
551 if (i2c_check_functionality(client->adapter,
552 I2C_FUNC_SMBUS_WRITE_I2C_BLOCK)) {
553 use_smbus_write = I2C_SMBUS_I2C_BLOCK_DATA;
554 } else if (i2c_check_functionality(client->adapter,
555 I2C_FUNC_SMBUS_WRITE_BYTE_DATA)) {
556 use_smbus_write = I2C_SMBUS_BYTE_DATA;
557 chip.page_size = 1;
558 }
559 }
560
561 if (chip.flags & AT24_FLAG_TAKE8ADDR)
562 num_addresses = 8;
563 else
564 num_addresses = DIV_ROUND_UP(chip.byte_len,
565 (chip.flags & AT24_FLAG_ADDR16) ? 65536 : 256);
566
567 at24 = devm_kzalloc(&client->dev, sizeof(struct at24_data) +
568 num_addresses * sizeof(struct i2c_client *), GFP_KERNEL);
569 if (!at24)
570 return -ENOMEM;
571
572 mutex_init(&at24->lock);
573 at24->use_smbus = use_smbus;
574 at24->use_smbus_write = use_smbus_write;
575 at24->chip = chip;
576 at24->num_addresses = num_addresses;
577
578 writable = !(chip.flags & AT24_FLAG_READONLY);
579 if (writable) {
580 if (!use_smbus || use_smbus_write) {
581
582 unsigned write_max = chip.page_size;
583
584 if (write_max > io_limit)
585 write_max = io_limit;
586 if (use_smbus && write_max > I2C_SMBUS_BLOCK_MAX)
587 write_max = I2C_SMBUS_BLOCK_MAX;
588 at24->write_max = write_max;
589
590 /* buffer (data + address at the beginning) */
591 at24->writebuf = devm_kzalloc(&client->dev,
592 write_max + 2, GFP_KERNEL);
593 if (!at24->writebuf)
594 return -ENOMEM;
595 } else {
596 dev_warn(&client->dev,
597 "cannot write due to controller restrictions.");
598 }
599 }
600
601 at24->client[0] = client;
602
603 /* use dummy devices for multiple-address chips */
604 for (i = 1; i < num_addresses; i++) {
605 at24->client[i] = i2c_new_dummy(client->adapter,
606 client->addr + i);
607 if (!at24->client[i]) {
608 dev_err(&client->dev, "address 0x%02x unavailable\n",
609 client->addr + i);
610 err = -EADDRINUSE;
611 goto err_clients;
612 }
613 }
614
615 at24->regmap_config.reg_bits = 32;
616 at24->regmap_config.val_bits = 8;
617 at24->regmap_config.reg_stride = 1;
618 at24->regmap_config.max_register = chip.byte_len - 1;
619
620 regmap = devm_regmap_init(&client->dev, &at24_regmap_bus, at24,
621 &at24->regmap_config);
622 if (IS_ERR(regmap)) {
623 dev_err(&client->dev, "regmap init failed\n");
624 err = PTR_ERR(regmap);
625 goto err_clients;
626 }
627
628 at24->nvmem_config.name = dev_name(&client->dev);
629 at24->nvmem_config.dev = &client->dev;
630 at24->nvmem_config.read_only = !writable;
631 at24->nvmem_config.root_only = true;
632 at24->nvmem_config.owner = THIS_MODULE;
633 at24->nvmem_config.compat = true;
634 at24->nvmem_config.base_dev = &client->dev;
635
636 at24->nvmem = nvmem_register(&at24->nvmem_config);
637
638 if (IS_ERR(at24->nvmem)) {
639 err = PTR_ERR(at24->nvmem);
640 goto err_clients;
641 }
642
643 i2c_set_clientdata(client, at24);
644
645 dev_info(&client->dev, "%u byte %s EEPROM, %s, %u bytes/write\n",
646 chip.byte_len, client->name,
647 writable ? "writable" : "read-only", at24->write_max);
648 if (use_smbus == I2C_SMBUS_WORD_DATA ||
649 use_smbus == I2C_SMBUS_BYTE_DATA) {
650 dev_notice(&client->dev, "Falling back to %s reads, "
651 "performance will suffer\n", use_smbus ==
652 I2C_SMBUS_WORD_DATA ? "word" : "byte");
653 }
654
655 /* export data to kernel code */
656 if (chip.setup)
657 chip.setup(at24->nvmem, chip.context);
658
659 return 0;
660
661err_clients:
662 for (i = 1; i < num_addresses; i++)
663 if (at24->client[i])
664 i2c_unregister_device(at24->client[i]);
665
666 return err;
667}
668
669static int at24_remove(struct i2c_client *client)
670{
671 struct at24_data *at24;
672 int i;
673
674 at24 = i2c_get_clientdata(client);
675
676 nvmem_unregister(at24->nvmem);
677
678 for (i = 1; i < at24->num_addresses; i++)
679 i2c_unregister_device(at24->client[i]);
680
681 return 0;
682}
683
684/*-------------------------------------------------------------------------*/
685
686static struct i2c_driver at24_driver = {
687 .driver = {
688 .name = "at24",
689 .acpi_match_table = ACPI_PTR(at24_acpi_ids),
690 },
691 .probe = at24_probe,
692 .remove = at24_remove,
693 .id_table = at24_ids,
694};
695
696static int __init at24_init(void)
697{
698 if (!io_limit) {
699 pr_err("at24: io_limit must not be 0!\n");
700 return -EINVAL;
701 }
702
703 io_limit = rounddown_pow_of_two(io_limit);
704 return i2c_add_driver(&at24_driver);
705}
706module_init(at24_init);
707
708static void __exit at24_exit(void)
709{
710 i2c_del_driver(&at24_driver);
711}
712module_exit(at24_exit);
713
714MODULE_DESCRIPTION("Driver for most I2C EEPROMs");
715MODULE_AUTHOR("David Brownell and Wolfram Sang");
716MODULE_LICENSE("GPL");
1/*
2 * at24.c - handle most I2C EEPROMs
3 *
4 * Copyright (C) 2005-2007 David Brownell
5 * Copyright (C) 2008 Wolfram Sang, Pengutronix
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License as published by
9 * the Free Software Foundation; either version 2 of the License, or
10 * (at your option) any later version.
11 */
12#include <linux/kernel.h>
13#include <linux/init.h>
14#include <linux/module.h>
15#include <linux/slab.h>
16#include <linux/delay.h>
17#include <linux/mutex.h>
18#include <linux/sysfs.h>
19#include <linux/mod_devicetable.h>
20#include <linux/log2.h>
21#include <linux/bitops.h>
22#include <linux/jiffies.h>
23#include <linux/of.h>
24#include <linux/i2c.h>
25#include <linux/platform_data/at24.h>
26
27/*
28 * I2C EEPROMs from most vendors are inexpensive and mostly interchangeable.
29 * Differences between different vendor product lines (like Atmel AT24C or
30 * MicroChip 24LC, etc) won't much matter for typical read/write access.
31 * There are also I2C RAM chips, likewise interchangeable. One example
32 * would be the PCF8570, which acts like a 24c02 EEPROM (256 bytes).
33 *
34 * However, misconfiguration can lose data. "Set 16-bit memory address"
35 * to a part with 8-bit addressing will overwrite data. Writing with too
36 * big a page size also loses data. And it's not safe to assume that the
37 * conventional addresses 0x50..0x57 only hold eeproms; a PCF8563 RTC
38 * uses 0x51, for just one example.
39 *
40 * Accordingly, explicit board-specific configuration data should be used
41 * in almost all cases. (One partial exception is an SMBus used to access
42 * "SPD" data for DRAM sticks. Those only use 24c02 EEPROMs.)
43 *
44 * So this driver uses "new style" I2C driver binding, expecting to be
45 * told what devices exist. That may be in arch/X/mach-Y/board-Z.c or
46 * similar kernel-resident tables; or, configuration data coming from
47 * a bootloader.
48 *
49 * Other than binding model, current differences from "eeprom" driver are
50 * that this one handles write access and isn't restricted to 24c02 devices.
51 * It also handles larger devices (32 kbit and up) with two-byte addresses,
52 * which won't work on pure SMBus systems.
53 */
54
55struct at24_data {
56 struct at24_platform_data chip;
57 struct memory_accessor macc;
58 int use_smbus;
59
60 /*
61 * Lock protects against activities from other Linux tasks,
62 * but not from changes by other I2C masters.
63 */
64 struct mutex lock;
65 struct bin_attribute bin;
66
67 u8 *writebuf;
68 unsigned write_max;
69 unsigned num_addresses;
70
71 /*
72 * Some chips tie up multiple I2C addresses; dummy devices reserve
73 * them for us, and we'll use them with SMBus calls.
74 */
75 struct i2c_client *client[];
76};
77
78/*
79 * This parameter is to help this driver avoid blocking other drivers out
80 * of I2C for potentially troublesome amounts of time. With a 100 kHz I2C
81 * clock, one 256 byte read takes about 1/43 second which is excessive;
82 * but the 1/170 second it takes at 400 kHz may be quite reasonable; and
83 * at 1 MHz (Fm+) a 1/430 second delay could easily be invisible.
84 *
85 * This value is forced to be a power of two so that writes align on pages.
86 */
87static unsigned io_limit = 128;
88module_param(io_limit, uint, 0);
89MODULE_PARM_DESC(io_limit, "Maximum bytes per I/O (default 128)");
90
91/*
92 * Specs often allow 5 msec for a page write, sometimes 20 msec;
93 * it's important to recover from write timeouts.
94 */
95static unsigned write_timeout = 25;
96module_param(write_timeout, uint, 0);
97MODULE_PARM_DESC(write_timeout, "Time (in ms) to try writes (default 25)");
98
99#define AT24_SIZE_BYTELEN 5
100#define AT24_SIZE_FLAGS 8
101
102#define AT24_BITMASK(x) (BIT(x) - 1)
103
104/* create non-zero magic value for given eeprom parameters */
105#define AT24_DEVICE_MAGIC(_len, _flags) \
106 ((1 << AT24_SIZE_FLAGS | (_flags)) \
107 << AT24_SIZE_BYTELEN | ilog2(_len))
108
109static const struct i2c_device_id at24_ids[] = {
110 /* needs 8 addresses as A0-A2 are ignored */
111 { "24c00", AT24_DEVICE_MAGIC(128 / 8, AT24_FLAG_TAKE8ADDR) },
112 /* old variants can't be handled with this generic entry! */
113 { "24c01", AT24_DEVICE_MAGIC(1024 / 8, 0) },
114 { "24c02", AT24_DEVICE_MAGIC(2048 / 8, 0) },
115 /* spd is a 24c02 in memory DIMMs */
116 { "spd", AT24_DEVICE_MAGIC(2048 / 8,
117 AT24_FLAG_READONLY | AT24_FLAG_IRUGO) },
118 { "24c04", AT24_DEVICE_MAGIC(4096 / 8, 0) },
119 /* 24rf08 quirk is handled at i2c-core */
120 { "24c08", AT24_DEVICE_MAGIC(8192 / 8, 0) },
121 { "24c16", AT24_DEVICE_MAGIC(16384 / 8, 0) },
122 { "24c32", AT24_DEVICE_MAGIC(32768 / 8, AT24_FLAG_ADDR16) },
123 { "24c64", AT24_DEVICE_MAGIC(65536 / 8, AT24_FLAG_ADDR16) },
124 { "24c128", AT24_DEVICE_MAGIC(131072 / 8, AT24_FLAG_ADDR16) },
125 { "24c256", AT24_DEVICE_MAGIC(262144 / 8, AT24_FLAG_ADDR16) },
126 { "24c512", AT24_DEVICE_MAGIC(524288 / 8, AT24_FLAG_ADDR16) },
127 { "24c1024", AT24_DEVICE_MAGIC(1048576 / 8, AT24_FLAG_ADDR16) },
128 { "at24", 0 },
129 { /* END OF LIST */ }
130};
131MODULE_DEVICE_TABLE(i2c, at24_ids);
132
133/*-------------------------------------------------------------------------*/
134
135/*
136 * This routine supports chips which consume multiple I2C addresses. It
137 * computes the addressing information to be used for a given r/w request.
138 * Assumes that sanity checks for offset happened at sysfs-layer.
139 */
140static struct i2c_client *at24_translate_offset(struct at24_data *at24,
141 unsigned *offset)
142{
143 unsigned i;
144
145 if (at24->chip.flags & AT24_FLAG_ADDR16) {
146 i = *offset >> 16;
147 *offset &= 0xffff;
148 } else {
149 i = *offset >> 8;
150 *offset &= 0xff;
151 }
152
153 return at24->client[i];
154}
155
156static ssize_t at24_eeprom_read(struct at24_data *at24, char *buf,
157 unsigned offset, size_t count)
158{
159 struct i2c_msg msg[2];
160 u8 msgbuf[2];
161 struct i2c_client *client;
162 unsigned long timeout, read_time;
163 int status, i;
164
165 memset(msg, 0, sizeof(msg));
166
167 /*
168 * REVISIT some multi-address chips don't rollover page reads to
169 * the next slave address, so we may need to truncate the count.
170 * Those chips might need another quirk flag.
171 *
172 * If the real hardware used four adjacent 24c02 chips and that
173 * were misconfigured as one 24c08, that would be a similar effect:
174 * one "eeprom" file not four, but larger reads would fail when
175 * they crossed certain pages.
176 */
177
178 /*
179 * Slave address and byte offset derive from the offset. Always
180 * set the byte address; on a multi-master board, another master
181 * may have changed the chip's "current" address pointer.
182 */
183 client = at24_translate_offset(at24, &offset);
184
185 if (count > io_limit)
186 count = io_limit;
187
188 switch (at24->use_smbus) {
189 case I2C_SMBUS_I2C_BLOCK_DATA:
190 /* Smaller eeproms can work given some SMBus extension calls */
191 if (count > I2C_SMBUS_BLOCK_MAX)
192 count = I2C_SMBUS_BLOCK_MAX;
193 break;
194 case I2C_SMBUS_WORD_DATA:
195 count = 2;
196 break;
197 case I2C_SMBUS_BYTE_DATA:
198 count = 1;
199 break;
200 default:
201 /*
202 * When we have a better choice than SMBus calls, use a
203 * combined I2C message. Write address; then read up to
204 * io_limit data bytes. Note that read page rollover helps us
205 * here (unlike writes). msgbuf is u8 and will cast to our
206 * needs.
207 */
208 i = 0;
209 if (at24->chip.flags & AT24_FLAG_ADDR16)
210 msgbuf[i++] = offset >> 8;
211 msgbuf[i++] = offset;
212
213 msg[0].addr = client->addr;
214 msg[0].buf = msgbuf;
215 msg[0].len = i;
216
217 msg[1].addr = client->addr;
218 msg[1].flags = I2C_M_RD;
219 msg[1].buf = buf;
220 msg[1].len = count;
221 }
222
223 /*
224 * Reads fail if the previous write didn't complete yet. We may
225 * loop a few times until this one succeeds, waiting at least
226 * long enough for one entire page write to work.
227 */
228 timeout = jiffies + msecs_to_jiffies(write_timeout);
229 do {
230 read_time = jiffies;
231 switch (at24->use_smbus) {
232 case I2C_SMBUS_I2C_BLOCK_DATA:
233 status = i2c_smbus_read_i2c_block_data(client, offset,
234 count, buf);
235 break;
236 case I2C_SMBUS_WORD_DATA:
237 status = i2c_smbus_read_word_data(client, offset);
238 if (status >= 0) {
239 buf[0] = status & 0xff;
240 buf[1] = status >> 8;
241 status = count;
242 }
243 break;
244 case I2C_SMBUS_BYTE_DATA:
245 status = i2c_smbus_read_byte_data(client, offset);
246 if (status >= 0) {
247 buf[0] = status;
248 status = count;
249 }
250 break;
251 default:
252 status = i2c_transfer(client->adapter, msg, 2);
253 if (status == 2)
254 status = count;
255 }
256 dev_dbg(&client->dev, "read %zu@%d --> %d (%ld)\n",
257 count, offset, status, jiffies);
258
259 if (status == count)
260 return count;
261
262 /* REVISIT: at HZ=100, this is sloooow */
263 msleep(1);
264 } while (time_before(read_time, timeout));
265
266 return -ETIMEDOUT;
267}
268
269static ssize_t at24_read(struct at24_data *at24,
270 char *buf, loff_t off, size_t count)
271{
272 ssize_t retval = 0;
273
274 if (unlikely(!count))
275 return count;
276
277 /*
278 * Read data from chip, protecting against concurrent updates
279 * from this host, but not from other I2C masters.
280 */
281 mutex_lock(&at24->lock);
282
283 while (count) {
284 ssize_t status;
285
286 status = at24_eeprom_read(at24, buf, off, count);
287 if (status <= 0) {
288 if (retval == 0)
289 retval = status;
290 break;
291 }
292 buf += status;
293 off += status;
294 count -= status;
295 retval += status;
296 }
297
298 mutex_unlock(&at24->lock);
299
300 return retval;
301}
302
303static ssize_t at24_bin_read(struct file *filp, struct kobject *kobj,
304 struct bin_attribute *attr,
305 char *buf, loff_t off, size_t count)
306{
307 struct at24_data *at24;
308
309 at24 = dev_get_drvdata(container_of(kobj, struct device, kobj));
310 return at24_read(at24, buf, off, count);
311}
312
313
314/*
315 * Note that if the hardware write-protect pin is pulled high, the whole
316 * chip is normally write protected. But there are plenty of product
317 * variants here, including OTP fuses and partial chip protect.
318 *
319 * We only use page mode writes; the alternative is sloooow. This routine
320 * writes at most one page.
321 */
322static ssize_t at24_eeprom_write(struct at24_data *at24, const char *buf,
323 unsigned offset, size_t count)
324{
325 struct i2c_client *client;
326 struct i2c_msg msg;
327 ssize_t status;
328 unsigned long timeout, write_time;
329 unsigned next_page;
330
331 /* Get corresponding I2C address and adjust offset */
332 client = at24_translate_offset(at24, &offset);
333
334 /* write_max is at most a page */
335 if (count > at24->write_max)
336 count = at24->write_max;
337
338 /* Never roll over backwards, to the start of this page */
339 next_page = roundup(offset + 1, at24->chip.page_size);
340 if (offset + count > next_page)
341 count = next_page - offset;
342
343 /* If we'll use I2C calls for I/O, set up the message */
344 if (!at24->use_smbus) {
345 int i = 0;
346
347 msg.addr = client->addr;
348 msg.flags = 0;
349
350 /* msg.buf is u8 and casts will mask the values */
351 msg.buf = at24->writebuf;
352 if (at24->chip.flags & AT24_FLAG_ADDR16)
353 msg.buf[i++] = offset >> 8;
354
355 msg.buf[i++] = offset;
356 memcpy(&msg.buf[i], buf, count);
357 msg.len = i + count;
358 }
359
360 /*
361 * Writes fail if the previous one didn't complete yet. We may
362 * loop a few times until this one succeeds, waiting at least
363 * long enough for one entire page write to work.
364 */
365 timeout = jiffies + msecs_to_jiffies(write_timeout);
366 do {
367 write_time = jiffies;
368 if (at24->use_smbus) {
369 status = i2c_smbus_write_i2c_block_data(client,
370 offset, count, buf);
371 if (status == 0)
372 status = count;
373 } else {
374 status = i2c_transfer(client->adapter, &msg, 1);
375 if (status == 1)
376 status = count;
377 }
378 dev_dbg(&client->dev, "write %zu@%d --> %zd (%ld)\n",
379 count, offset, status, jiffies);
380
381 if (status == count)
382 return count;
383
384 /* REVISIT: at HZ=100, this is sloooow */
385 msleep(1);
386 } while (time_before(write_time, timeout));
387
388 return -ETIMEDOUT;
389}
390
391static ssize_t at24_write(struct at24_data *at24, const char *buf, loff_t off,
392 size_t count)
393{
394 ssize_t retval = 0;
395
396 if (unlikely(!count))
397 return count;
398
399 /*
400 * Write data to chip, protecting against concurrent updates
401 * from this host, but not from other I2C masters.
402 */
403 mutex_lock(&at24->lock);
404
405 while (count) {
406 ssize_t status;
407
408 status = at24_eeprom_write(at24, buf, off, count);
409 if (status <= 0) {
410 if (retval == 0)
411 retval = status;
412 break;
413 }
414 buf += status;
415 off += status;
416 count -= status;
417 retval += status;
418 }
419
420 mutex_unlock(&at24->lock);
421
422 return retval;
423}
424
425static ssize_t at24_bin_write(struct file *filp, struct kobject *kobj,
426 struct bin_attribute *attr,
427 char *buf, loff_t off, size_t count)
428{
429 struct at24_data *at24;
430
431 if (unlikely(off >= attr->size))
432 return -EFBIG;
433
434 at24 = dev_get_drvdata(container_of(kobj, struct device, kobj));
435 return at24_write(at24, buf, off, count);
436}
437
438/*-------------------------------------------------------------------------*/
439
440/*
441 * This lets other kernel code access the eeprom data. For example, it
442 * might hold a board's Ethernet address, or board-specific calibration
443 * data generated on the manufacturing floor.
444 */
445
446static ssize_t at24_macc_read(struct memory_accessor *macc, char *buf,
447 off_t offset, size_t count)
448{
449 struct at24_data *at24 = container_of(macc, struct at24_data, macc);
450
451 return at24_read(at24, buf, offset, count);
452}
453
454static ssize_t at24_macc_write(struct memory_accessor *macc, const char *buf,
455 off_t offset, size_t count)
456{
457 struct at24_data *at24 = container_of(macc, struct at24_data, macc);
458
459 return at24_write(at24, buf, offset, count);
460}
461
462/*-------------------------------------------------------------------------*/
463
464#ifdef CONFIG_OF
465static void at24_get_ofdata(struct i2c_client *client,
466 struct at24_platform_data *chip)
467{
468 const __be32 *val;
469 struct device_node *node = client->dev.of_node;
470
471 if (node) {
472 if (of_get_property(node, "read-only", NULL))
473 chip->flags |= AT24_FLAG_READONLY;
474 val = of_get_property(node, "pagesize", NULL);
475 if (val)
476 chip->page_size = be32_to_cpup(val);
477 }
478}
479#else
480static void at24_get_ofdata(struct i2c_client *client,
481 struct at24_platform_data *chip)
482{ }
483#endif /* CONFIG_OF */
484
485static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
486{
487 struct at24_platform_data chip;
488 bool writable;
489 int use_smbus = 0;
490 struct at24_data *at24;
491 int err;
492 unsigned i, num_addresses;
493 kernel_ulong_t magic;
494
495 if (client->dev.platform_data) {
496 chip = *(struct at24_platform_data *)client->dev.platform_data;
497 } else {
498 if (!id->driver_data)
499 return -ENODEV;
500
501 magic = id->driver_data;
502 chip.byte_len = BIT(magic & AT24_BITMASK(AT24_SIZE_BYTELEN));
503 magic >>= AT24_SIZE_BYTELEN;
504 chip.flags = magic & AT24_BITMASK(AT24_SIZE_FLAGS);
505 /*
506 * This is slow, but we can't know all eeproms, so we better
507 * play safe. Specifying custom eeprom-types via platform_data
508 * is recommended anyhow.
509 */
510 chip.page_size = 1;
511
512 /* update chipdata if OF is present */
513 at24_get_ofdata(client, &chip);
514
515 chip.setup = NULL;
516 chip.context = NULL;
517 }
518
519 if (!is_power_of_2(chip.byte_len))
520 dev_warn(&client->dev,
521 "byte_len looks suspicious (no power of 2)!\n");
522 if (!chip.page_size) {
523 dev_err(&client->dev, "page_size must not be 0!\n");
524 return -EINVAL;
525 }
526 if (!is_power_of_2(chip.page_size))
527 dev_warn(&client->dev,
528 "page_size looks suspicious (no power of 2)!\n");
529
530 /* Use I2C operations unless we're stuck with SMBus extensions. */
531 if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
532 if (chip.flags & AT24_FLAG_ADDR16)
533 return -EPFNOSUPPORT;
534
535 if (i2c_check_functionality(client->adapter,
536 I2C_FUNC_SMBUS_READ_I2C_BLOCK)) {
537 use_smbus = I2C_SMBUS_I2C_BLOCK_DATA;
538 } else if (i2c_check_functionality(client->adapter,
539 I2C_FUNC_SMBUS_READ_WORD_DATA)) {
540 use_smbus = I2C_SMBUS_WORD_DATA;
541 } else if (i2c_check_functionality(client->adapter,
542 I2C_FUNC_SMBUS_READ_BYTE_DATA)) {
543 use_smbus = I2C_SMBUS_BYTE_DATA;
544 } else {
545 return -EPFNOSUPPORT;
546 }
547 }
548
549 if (chip.flags & AT24_FLAG_TAKE8ADDR)
550 num_addresses = 8;
551 else
552 num_addresses = DIV_ROUND_UP(chip.byte_len,
553 (chip.flags & AT24_FLAG_ADDR16) ? 65536 : 256);
554
555 at24 = devm_kzalloc(&client->dev, sizeof(struct at24_data) +
556 num_addresses * sizeof(struct i2c_client *), GFP_KERNEL);
557 if (!at24)
558 return -ENOMEM;
559
560 mutex_init(&at24->lock);
561 at24->use_smbus = use_smbus;
562 at24->chip = chip;
563 at24->num_addresses = num_addresses;
564
565 /*
566 * Export the EEPROM bytes through sysfs, since that's convenient.
567 * By default, only root should see the data (maybe passwords etc)
568 */
569 sysfs_bin_attr_init(&at24->bin);
570 at24->bin.attr.name = "eeprom";
571 at24->bin.attr.mode = chip.flags & AT24_FLAG_IRUGO ? S_IRUGO : S_IRUSR;
572 at24->bin.read = at24_bin_read;
573 at24->bin.size = chip.byte_len;
574
575 at24->macc.read = at24_macc_read;
576
577 writable = !(chip.flags & AT24_FLAG_READONLY);
578 if (writable) {
579 if (!use_smbus || i2c_check_functionality(client->adapter,
580 I2C_FUNC_SMBUS_WRITE_I2C_BLOCK)) {
581
582 unsigned write_max = chip.page_size;
583
584 at24->macc.write = at24_macc_write;
585
586 at24->bin.write = at24_bin_write;
587 at24->bin.attr.mode |= S_IWUSR;
588
589 if (write_max > io_limit)
590 write_max = io_limit;
591 if (use_smbus && write_max > I2C_SMBUS_BLOCK_MAX)
592 write_max = I2C_SMBUS_BLOCK_MAX;
593 at24->write_max = write_max;
594
595 /* buffer (data + address at the beginning) */
596 at24->writebuf = devm_kzalloc(&client->dev,
597 write_max + 2, GFP_KERNEL);
598 if (!at24->writebuf)
599 return -ENOMEM;
600 } else {
601 dev_warn(&client->dev,
602 "cannot write due to controller restrictions.");
603 }
604 }
605
606 at24->client[0] = client;
607
608 /* use dummy devices for multiple-address chips */
609 for (i = 1; i < num_addresses; i++) {
610 at24->client[i] = i2c_new_dummy(client->adapter,
611 client->addr + i);
612 if (!at24->client[i]) {
613 dev_err(&client->dev, "address 0x%02x unavailable\n",
614 client->addr + i);
615 err = -EADDRINUSE;
616 goto err_clients;
617 }
618 }
619
620 err = sysfs_create_bin_file(&client->dev.kobj, &at24->bin);
621 if (err)
622 goto err_clients;
623
624 i2c_set_clientdata(client, at24);
625
626 dev_info(&client->dev, "%zu byte %s EEPROM, %s, %u bytes/write\n",
627 at24->bin.size, client->name,
628 writable ? "writable" : "read-only", at24->write_max);
629 if (use_smbus == I2C_SMBUS_WORD_DATA ||
630 use_smbus == I2C_SMBUS_BYTE_DATA) {
631 dev_notice(&client->dev, "Falling back to %s reads, "
632 "performance will suffer\n", use_smbus ==
633 I2C_SMBUS_WORD_DATA ? "word" : "byte");
634 }
635
636 /* export data to kernel code */
637 if (chip.setup)
638 chip.setup(&at24->macc, chip.context);
639
640 return 0;
641
642err_clients:
643 for (i = 1; i < num_addresses; i++)
644 if (at24->client[i])
645 i2c_unregister_device(at24->client[i]);
646
647 return err;
648}
649
650static int at24_remove(struct i2c_client *client)
651{
652 struct at24_data *at24;
653 int i;
654
655 at24 = i2c_get_clientdata(client);
656 sysfs_remove_bin_file(&client->dev.kobj, &at24->bin);
657
658 for (i = 1; i < at24->num_addresses; i++)
659 i2c_unregister_device(at24->client[i]);
660
661 return 0;
662}
663
664/*-------------------------------------------------------------------------*/
665
666static struct i2c_driver at24_driver = {
667 .driver = {
668 .name = "at24",
669 .owner = THIS_MODULE,
670 },
671 .probe = at24_probe,
672 .remove = at24_remove,
673 .id_table = at24_ids,
674};
675
676static int __init at24_init(void)
677{
678 if (!io_limit) {
679 pr_err("at24: io_limit must not be 0!\n");
680 return -EINVAL;
681 }
682
683 io_limit = rounddown_pow_of_two(io_limit);
684 return i2c_add_driver(&at24_driver);
685}
686module_init(at24_init);
687
688static void __exit at24_exit(void)
689{
690 i2c_del_driver(&at24_driver);
691}
692module_exit(at24_exit);
693
694MODULE_DESCRIPTION("Driver for most I2C EEPROMs");
695MODULE_AUTHOR("David Brownell and Wolfram Sang");
696MODULE_LICENSE("GPL");